1. Field of the Invention
The present invention relates to a portable electronic device, a so-called IC card, which incorporates an IC (integrated circuit) chip having, e.g., a nonvolatile memory, and a control element such as a CPU and, more particularly, to a management method of a user area of the memory.
2. Description of the Related Art
In recent years, a so-called IC card which incorporates an IC chip having an erasable nonvolatile memory, and a control element such as a CPU has received a lot of attention as a new portable data storage medium. In an IC card of this type, an internal memory is accessed by an internal control element to selectively input/output data from/to an external device.
Recently, as the life cycle of such IC cards has been clarified, a card issuer often wants to register a constituting element such as an area or a data file designed by himself in an IC card. In this case, an operation of memory cells in a specific open area in a memory must be checked.
In this case, in one method, externally input optional data may be received and written in a predetermined area, and a memory cell error may be determined in accordance with the processing result. According to this method, however, it is not easy to find malfunctions of address and data bus signals supplied to the memory.
In another method, externally input optional data (e.g., increment data starting from "00") may be supplied to an IC card, and it may be checked if the data can be written in a memory. However, it is preferable that data in the memory has been initialized in the subsequent area registration mode.
In still another method, externally input optional data may be received, and may be written in a predetermined region or may be verified to check memory cells. However, if verification is able to be performed after area registration, this poses a problem in terms of security.